From 2001-2002 to 2007-2008, the median level of perchlorate in urine among women ages 16 to 49 years was 3 µg/L with little variation over time. Over the same period, the 95th percentile varied between 13 and 17 µg/L.

In 2005-2008, there was little variation in median or 95th percentile perchlorate levels by race/ethnicity or income among women ages 16 to 49 years. (See Tables B13a and B13b (PDF). (4pp, 463K, About PDF))

From 2001-2002 to 2007-2008, the median level of perchlorate among children ages 6 to 17 years was 5 µg/L with little variation over time. The 95th percentile perchlorate level among children increased from 15 µg/L in 2001-2002 to 19 µg/L in 2007-2008. (See Tables B13c (PDF). (4pp, 463K, About PDF))

The median perchlorate level among children ages 6 to 17 years was about 42% higher than the level found in women of childbearing age in 2005-2008, while the 95th percentile level among children ages 6 to 17 years was about 19% higher than in women of childbearing age. (See Tables B13 and B13c (PDF). (4pp, 463K, About PDF))

There were minimal differences in urinary perchlorate levels by age group among children ages 6 to 17 years. (See Tables B13f (PDF). (4pp, 463K, About PDF))

About the Perchlorate Indicator

Indicator B13 presents information about perchlorate levels measured in women. The data are from a national survey that collects urine specimens from a representative sample of the population every two years, and then measures the concentration of various contaminants in urine. The indicator focuses on women of child-bearing age because of concern for potential adverse effects in children born to women who have been exposed to perchlorate.

Indicator B13 presents concentrations of perchlorate in urine of women ages 16 to 49 years from 2001-2008.

Perchlorate is a naturally occurring and man-made chemical that is used to manufacture fireworks, explosives, flares, and rocket fuel. It is found naturally in groundwater and soils throughout many arid regions; and has been detected in surface water, dairy products, and some food crops. Perchlorate has also been detected in bodily fluids like human breast milk, urine, blood, amniotic fluid, and saliva. It has also been found in some infant formulas.

Exposure to high doses of perchlorate has been shown to block the uptake of iodide into the thyroid gland. This is of particular concern for women of child-bearing age, because thyroid hormones are important for growth and development of the central nervous system in fetuses and infants. Moderate deficits in maternal thyroid hormone levels during early pregnancy have been linked to reduced childhood IQ scores and other neurodevelopmental effects. In 2005, the National Research Council (NRC) concluded that the available epidemiological evidence did not indicate an association with thyroid disorders in adults or infants, and was inadequate for assessing the potential for adverse associations between prenatal perchlorate exposure and adverse neurodevelopmental outcomes in children. The NRC also noted a lack of studies to evaluate potential effects of prenatal perchlorate exposures in infants and children, particularly in vulnerable populations.

Indicator B13 presents perchlorate levels measured in urine of women from the National Health and Nutrition Examination Survey (NHANES).

Summary of Methods - Perchlorate

The National Center for Health Statistics, a division of the Centers for Disease Control and Prevention, conducts the National Health and Nutrition Examination Surveys (NHANES), a series of U.S. national surveys of the health and nutrition status of the noninstitutionalized civilian population. Interviews and physical examinations are conducted with approximately 10,000 people in each two-year survey cycle. The survey measures perchlorate levels in urine samples collected from NHANES participants.